Hand washing sinks and basins are used in many different environments. The water discharge device used in connection with the sink/basin is typically selected to suit the environment in which the sink/basin is located. For instance, in medical applications in which hygiene is of importance it is desirable to minimize the transfer and growth of bacterial colonies within the water delivery system components.
A variety of water discharge devices have been designed to minimize cross contamination by removing the need for direct hand contact to operate the necessary valves. This type of water discharge device is often referred to as a “hands-free tap”. Examples of hands-free taps include arm-operated faucet levers, and foot operated valves. Increasingly, sensor actuated valves are being used in water discharge devices so that users need only place their hands near the sensor, rather than physically contacting any components of the device.
Typical industries where minimizing cross contamination is desirable include:                food preparation or food manufacturing;        hospital wards;        wash or scrub room that leads into the operating theatre;        doctor or dentist rooms;        change locks for clean rooms; and        medical rooms at sporting clubs and schools.        
However, cross contamination can still occur using hands-free taps by users touching the tap fluid outlet chamber, or by airborne contamination entering the moist or wet tap fluid outlet chamber which is an ideal site for harbouring and growth of contamination.
In current technology, residual moisture and stagnant water remains within the spouts of water delivery devices between uses. Studies show that this stagnant water or moisture is readily contaminated by physical contact or by airborne contaminants entering the tap outlet spout. The stagnant water can form a stable “biofilm” on the internal lining surfaces of the spout within which pathogens and opportunistic bacteria will grow. Bacteria in the biofilm can slough off contamination randomly, contaminating discharged water, while continually replenishing itself.
Studies have shown that the “still standing” tap water in hands free taps can provide nearly ideal growth conditions for Pseudomonas aeruginosa. This is a significant problem for Intensive Care Units and burns centres. Contaminated spouts have also been shown to cause cross-transmission of other dangerous organisms, such as Legionella ssp.
There is a need for water discharge devices that can reduce the microbial contamination of discharged water.